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Re: Feedback/impressions on the PhD-M6 custom battery pack

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by LuxLuthor

Thanks for doing this. I wonder if there is a way to get this into a format for printing landscape on 8.5 x 11 paper, and/or put on Excel to add lines to track entire line easier? It takes a while to compare some of this to other tested results. That being said, I'm not sure I agree with all your numbers (i.e. recommended voltage range & lumens--for example the 1111), but it is still a useful comparative reference, and represents a good bit of work. Where are you getting your lumens readings from? Do we have CBA-II test results running the AW 17670 at various Amp loads? If not, I can do that quickly.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by donn_

It automatically printed in landscape for me.

I know it is designed, displays, and prints in landscape.

Unless you shrink it to force fitting onto letter size, which makes it uber small, it doesn't print the sides. All that is needed is to shorten the titles, or put them on two lines to not waste all the space. A document with this many items and colums also needs lines to follow accross.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Do you want the image or the actual xls file? If the latter, I need a site to upload it. If the former, I can convert the Excel page to a jpeg or whatever, put it on photobucket, and put it into a post to the thread.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by Justin Case

Do you want the image or the actual xls file? If the latter, I need a site to upload it. If the former, I can convert the Excel page to a jpeg or whatever, put it on photobucket, and put it into a post to the thread.

I am hosting all of the pictures and files already, including this file from Eric. If you email me the file, I will host it along with the original file.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by oldways

Guys

At 9v would the MN61 be producing 400 or more otf?

As you probably remember from the development and feeler threads I did a lot of runtime tests on the MN21, but the cells always came out too darn hot from the continuous run (of course not recommended, but it was part of my development/tests). The MN61 sounds like a fantastic match to the cell chemistry that we have today, so I am definitely going to give it a try today or tomorrow.

If it would help any of you on the fence, and since I have two M6's, I could do a side-by-side beamshot at night comparing both the MN21 and the MN61.

Re: Feedback/impressions on the PhD-M6 custom battery pack

I just finished running AW 17670 discharge graphs at 1, 2, 3, 4, 5 Amps with the cells I have, and as a result will be making another change to my custom profile Level 4, giving up on the 10.8V category. I should have thought about this aspect earlier.

I took the time to go back through my PayPal transactions to see that I bought my only six 17670 AW protected cells way back in May, 2007, so people need to consider the age of these cells with my posted results, as newer ones may perform better. I sent a PM to AW to look at these results, and comment.

Edit: I'm dropping my 10.8V setting because if we divide that by 3, we get 3.6V per cell. So the question is whether a specific bulb being driven at its necessary Amp level will have the cell voltage held above 3.6V for a reasonable amount of time. The 1185 draws 3.4A itself (not including additional drain from pack resistance), and you can see the green line above is all below 3.6V...so this would make it out of regulation==>going to direct drive.

Even the 1331 @ 10.8V uses 2.1A for the bulb alone. You can see how quickly the 2A red line crosses the 3.6V threshold.

Now looking at the 1164 @ 9.3V uses 4.2Amps, but now we have a lower voltage threshold (9.3V/3 = 3.1V/cell) before it drops below regulation. It crosses the 3.1V line just short of 1Ah which is better than nothing.

Suffice it to say that I'm going back to the drawing board. I don't know how much "beefier" the newest AW 17670-P cells are, but I would rather err on the conservative side.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by LuxLuthor

I just finished running AW 17670 discharge graphs at 1, 2, 3, 4, 5 Amps with the cells I have, and as a result will be making another change to my custom profile Level 4, giving up on the 10.8V category. I should have thought about this aspect earlier.

I took the time to go back through my PayPal transactions to see that I bought my only six 17670 AW protected cells way back in May, 2007, so people need to consider the age of these cells with my posted results, as newer ones may perform better. I sent a PM to AW to look at these results, and comment.

Wow you're right, it can't sustain very much voltage when draw is over 2-3 amps. The good news is, the king of throw among the M6 bulbs in my experience (outside the 1185) is the HO-M6R at only 2.1amps. It smokes the MN21 and even beats the WA1111 by a small margin. There's no way I would give up my 10.8v setting and the ability to run this bulb with this pack, even if it will drop out of regulation quickly. The low amp draw, low heat, excellent reach, beautiful beam pattern and long bulb life are just too good not to have a setting for. The IMR-M6 is another reason to keep the 10.8v setting IMO.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by LuxLuthor

I just finished running AW 17670 discharge graphs at 1, 2, 3, 4, 5 Amps with the cells I have, and as a result will be making another change to my custom profile Level 4, giving up on the 10.8V category. I should have thought about this aspect earlier.

I took the time to go back through my PayPal transactions to see that I bought my only six 17670 AW protected cells way back in May, 2007, so people need to consider the age of these cells with my posted results, as newer ones may perform better. I sent a PM to AW to look at these results, and comment.

It looks like ~2A draw (1.25C) from the AW17670s is a reasonable max in terms of holding cell voltage under load. What this might translate to for PWM...?

A WA01331 might be able to run in regulation at 10.8V for say 10 min before going direct drive for the remainder of the battery pack's capacity.

My two workhorse bulb candidates are the MN15 and WA01274, for lower output/longer run time and higher output/moderate run time options, respectively. If I didn't have an FM MN bi-pin adapter and a bunch of 1274s already, I might go with an MN15 and MN61.

I'm taking a slight chance with my Level 3 at 8.0V for the 1274. But I can always run the bulb at Level 2 at 7.3V. At $5 per bulb, the 1274 looks like a good all-around choice to me.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by RichS

Wow you're right, it can't sustain very much voltage when draw is over 2-3 amps. The good news is, the king of throw among the M6 bulbs in my experience (outside the 1185) is the HO-M6R at only 2.1amps. It smokes the MN21 and even beats the WA1111 by a small margin. There's no way I would give up my 10.8v setting and the ability to run this bulb with this pack, even if it will drop out of regulation quickly. The low amp draw, low heat, excellent reach, beautiful beam pattern and long bulb life are just too good not to have a setting for. The IMR-M6 is another reason to keep the 10.8v setting IMO.

Rich, I don't have much objective data with the MN & Lighthound bulbs, but I'm confused by your saying the HO-M6R "smokes the MN21," when I see Eric's chart listing it as only 400L diminishing to 250L, vs. his report of the MN21 being 500-700L. I'm also not clear on how he got his lumen readings, and whether they are "bulb lumens," or extrapolated "Torch lumens" (using the 65% x Bulb Lumen formula that I have never accepted).

Too many questions....and miles to go before I sleep. Miles to go before I sleep.

Edit: Now I see where you are getting that from. When I look at my box of the HO-M6R, it's spec is 700L @ 13V. Ain't gonna get up there with these cells.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by LuxLuthor

Rich, I don't have much objective data with the MN & Lighthound bulbs, but I'm confused by your saying the HO-M6R "smokes the MN21," when I see Eric's chart listing it as only 400L diminishing to 250L, vs. his report of the MN21 being 500-700L. I'm also not clear on how he got his lumen readings, and whether they are "bulb lumens," or extrapolated "Torch lumens" (using the 65% x Bulb Lumen formula that I have never accepted).

Too many questions....and miles to go before I sleep. Miles to go before I sleep.

Very fair question Lux. This is based upon the results of beamshot tests I did a while back with the M6. To be clear, I was referencing the throw of the HO-M6R per the prior statement. I'm not disagreeing that the MN21 puts out more overall lumens. Now, the "smokes" part came from testing the MN21 on fresh primaries (stock SureFire config) vs. the HO-M6R. However, it also beat the MN21 by a smaller margin even when run the MN21 was run on fully charged 18650s. Again, it beat it in overall throw, not total lumens. With a light of this form factor, throw is one of my major considerations in a lamp for the M6. And in that department, the HO-M6R wins (and maintains it's practicality at the same time ).

Re: Feedback/impressions on the PhD-M6 custom battery pack

Right, but remember that 13V 700L HO setup is designed for 6 x RCR123A which has no relationship to 3 x 17670. It seems the most practical use of that bulb is with direct drive 6 x RCR123A, but I'm not that experienced with using it yet.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by LuxLuthor

Right, but remember that 13V 700L HO setup is designed for 6 x RCR123A which has no relationship to 3 x 17670. It seems the most practical use of that bulb is with direct drive 6 x RCR123A, but I'm not that experienced with using it yet.

Incorrect, the standard M6 battery holder is 3s2p so in this case the 3 x 17670 is perfectly matched to the HO-M6R. In fact, the HO-M6R is really the best basic setup for the 3 x 17670.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Incorrect, the standard M6 battery holder is 3s2p so in this case the 3 x 17670 is perfectly matched to the HO-M6R. In fact, the HO-M6R is really the best basic setup for the 3 x 17670.

Oh yeah, right. I always forget that pesky little 3s2p battery holder detail, thanks! I keep saying, I have not used many of the M6 MN or Lighthound bulbs, nor RCR123 cells, so I should shut up on those specifics, and go back to Eric's chart for them. Sorry for the confusion.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by Justin Case

really none of these HO bulbs -- e.g., 5761, 1185, 5607 -- are all that practical. They all require fairly high current and 3x17670 in whatever chemistry is just going to be limited in feeding that appetite.

Greetings Justin,

So very true....

The good new is that, due to the efficiency gains from lower resistance in IMR cells, the lower capacity will not translate to as much runtime loss as one would think on many of these bulbs. I actually ran the numbers for an MN21 on a theoretical IMR17670 pack and came up with a 17% drop in runtime, but it would be more consistent from run to run and survive hundreds of cycles safely.

------------

Originally Posted by LuxLuthor

I wonder if there is a way to get this into a format for printing landscape on 8.5 x 11 paper, and/or put on Excel to add lines to track entire line easier?

Howdy Luxluthor!

I actually tried to get it to leave the lines in the PDF export from the spreadsheet but couldn't find a way to do it, (using NeoOffice). I'm not a big fan of crossing my fingers that everyone will have the ability to open a spreadsheet file created by one of the many "office" packages out there. Hard to find someone who doesn't have a PDF reader though, and PDF files produce predictable printing behavior.

I'm not sure I agree with all your numbers (i.e. recommended voltage range & lumens--for example the 1111), but it is still a useful comparative reference, and represents a good bit of work. Where are you getting your lumens readings from?

Well, I've been referencing the charts that you made for these numbers since way back when you did them and using modified re-rate formulas that more closely mimic actual measured lux from your charts. They represent the most accurate estimated bulb lumen figures available for a wide array of drive levels anywhere. The CPF community and myself owe you more thanks than can possibly be given for this information. The chart was developed because it offers PhD-M6 customers a fast reference general guideline for making decisions about bulbs and drive levels. The PhD-M6 product could probably be sold without any such chart available, leaving folks to "fend for themselves" so to speak. I wanted to provide at least something to give a guideline that I feel comfortable with for the scope of this project.

For the KT4 style Millennium Turbo Head, I believe that the 65% loss is appropriate, so that is what has been applied. I am in agreement with you that 65% torch conversion is not always accurate. I believe that a well made head that does not take losses to a foam insert and recessed shock absorption system can achieve better numbers. You and I both know that light is perceived in a logarithmic fashion, so rough numbers are more than adequate.

Of course, I am quite confident, that many people will read the chart, and completely ignore the qualifier words highlighted in the top row, "estimated" , "approximate" etc. Someone will want to hold me to the grinding stone, for them, I say the following: Sign a contract to purchase 10,000 units, I will arrange to provide accurate measured output for every bulb at a variety of drive levels With the amount of work that has gone into this project, there isn't much of a selling price that will ever completely cover every hour. Even with such testing, there would be no way to guarantee specific lumen outputs on flashlights. There are too many variables. All it takes is for 1 contact to be slightly gunked up or oxidized, and the numbers all fall apart.

Keep in mind, that a particular voltage does not hold true from one test rig to the next. Are we talking V-Batt? V-Bulb, V-Springs, V-half-way in-betwen, V-Pack..? The PhD-M6 is calibrated with a test rig that fairly closely mimics the resistance that could be expected in a properly cleaned and cared for M6 flashlight. So When I recommend 6.8V or 7.2V, or whatever, I'm not talking about V-pack voltage, we're basically at the base of the spring contacts for the bulb. The difference can be dramatic, a few percent different in voltage can equate to 10% or more actual output. I've thought as much of this through as anyone could be expected to and come up with what I believe are reasonable approximations with the information I have.

------------

Originally Posted by oldways

At 9v would the MN61 be producing 400 or more otf?

Hi oldways,

Unless someone wants to measure it in a sphere, I can not guarantee anything, I would estimate that it should be somewhere around 400 torch lumens at 9V. Remember those "qualifying" words in the chart.

The reality is that, the difference between 350 and 450 lumens is pretty hard to see. If it's in the ballpark of a need, then it will work.

It's not like someone is going to be spotting something with a 385 lumen light, and have a hard time seeing it, say to their friend, "gosh darn-it, I should have bought the 415 lumen version!"

Of course, some people might think that it would have made a difference, but the truth of the matter is, that beam profile has a larger impact on useful performance for an application within a ball park lumen range than the lumens themselves.

-------------

Originally Posted by Justin Case

I'll send the xls file momentarily.

Thank You Justin for converting the file. It looks great!

-------------

Originally Posted by oldways

Looking at the bulb chart the MN61 looks like the one to run.

If it is 400+ otf at 9v would be a very useful setup capable of sustained runs.

I would love to see beamhots of the MN21 and MN61 sxs.

Also wonder how it would do at 9.2-9.3v?

Hi oldways[/quote]

I am going to run some more numbers and try to come up with some better figures for the MN61 and MN60, I realized after building the chart that I haven't taken into account the lower losses from resistance on the higher voltage bulbs entirely on that chart for these bulbs. 9.2V may be more appropriate for a good overall performance on the MN61. Keep in mind, that the closer one gets to ~10V drive levels, the harder it is to ensure regulation though the discharge.

Stay tuned, I may change the ranges and values for some bulbs in the coming days. Of course, it's still all just very educated guess work, but I'll do the best I can. {wink wink}

-----------

Originally Posted by LuxLuthor

I just finished running AW 17670 discharge graphs at 1, 2, 3, 4, 5 Amps with the cells I have, and as a result will be making another change to my custom profile Level 4, giving up on the 10.8V category. I should have thought about this aspect earlier.

As you may have noticed, I've been pointing out since doing testing that the 10.8V setting just isn't going to provide much if any regulation for most bulbs. It's hard to articulate why, but I'll go ahead and throw out some numbers for folks to consider:

That's equates to 10.9V to an 1185 with AW17670s in good condition and good clean contacts. It only takes a few seconds to drop out of regulation.

This calculation assumes that the electrolytic reaction keeps up 100% with the rate demanded. There are losses there that are very hard to quantify being heavily dependent on temperature.

I bought my only six 17670 AW protected cells way back in May, 2007, so people need to consider the age of these cells with my posted results, as newer ones may perform better.

I've noticed a difference in runtime just by going from cells purchased about 1-1.5 year ago to cells that just arrived a few days ago. Cell age and condition are critical factors way outside our control.

Originally Posted by LuxLuthor

Even the 1331 @ 10.8V uses 2.1A for the bulb alone. You can see how quickly the 2A red line crosses the 3.6V threshold.

Yes, after taking the 2% loss from the maximum duty cycle we can run, and added resistance from contacts and such, even the 1331 and HO-M6R will not run in regulation. If they do, it isn't for long.

Originally Posted by LuxLuthor

Suffice it to say that I'm going back to the drawing board. I don't know how much "beefier" the newest AW 17670-P cells are, but I would rather err on the conservative side.

The newer the better. I'm actually surprised to see that you got ~1.4AH from ~3 year old cells. Brand new cells are pretty close to 1.6AH. The actual stored energy is even more, but it's not usable energy unless they are drained infinitely slow. The way in which cells are used or stored over the years can have quite the impact. My ~1 year old cells probably wouldn't perform much better than your test results.

Speaking of test results, THANK YOU!!! It can not be repeated enough, you're a treasure for CPF. Keep up the good work!

---------------

Originally Posted by RichS

The good news is, the king of throw among the M6 bulbs in my experience (outside the 1185) is the HO-M6R at only 2.1amps. It smokes the MN21 and even beats the WA1111 by a small margin. There's no way I would give up my 10.8v setting and the ability to run this bulb with this pack, even if it will drop out of regulation quickly. The low amp draw, low heat, excellent reach, beautiful beam pattern and long bulb life are just too good not to have a setting for. The IMR-M6 is another reason to keep the 10.8v setting IMO.

When comparing direct drive options, the HO-M6R is definitely a King of bulb options. It, like any other bulb in direct drive, suffers diminishing output through the discharge. but since other bulbs suffer the same, it wins in many contests.

Within the context of the PhD-M6, the HO-M6R does not win very many contests. Keep in mind that we have more contacts between the cells and the bulb as a result of the regulator being part of the circuit. We also have a 2% voltage loss purely due to the fact that the regulator can never operate at 100% duty cycle and still take proper voltage measurements for moon mode and attempted regulation.

I am personally a huge fan of the HO-M6R when direct driven on a nice low resistance 3xli-ion cell configuration. It's my #1 choice bulb for 3 cells. The PhD-M6 introduces a scenario where the HO-M6R doesn't hold it's ground against other options anywhere near as well.

With regulation, the MN21 at 6.8V walks all over the HO-M6R in pretty much any contest. Even the IMR-M3T looks better at 7.5V than the HO-M6R if compared as an "average" through the discharge (both rated the same "700" bulb lumen). The HO-M6R is hard to beat for it's tight beam pattern, but the raw punch behind it fades quickly when compared to a regulated configuration.

-----------

Originally Posted by Justin Case

It looks like ~2A draw (1.25C) from the AW17670s is a reasonable max in terms of holding cell voltage under load. What this might translate to for PWM...?

Hi Justin,

Post #56 in this thread by myself gives an example of the effects of PWM. The truth is, there isn't any way for me to articulate the effects of PWM without a lot of math. The translation that does not require math for the end user can be found in the "heat factor" rating in the chart that I posted before. The "heat factor" rating is like a comparison between what would have been a direct drive 2C discharge, and the effects of the PWM load presented here with different bulbs.

Originally Posted by Justin Case

A WA01331 might be able to run in regulation at 10.8V for say 10 min before going direct drive for the remainder of the battery pack's capacity.

Originally, I had suspected that it might be possible to have some worthwhile regulation in the 10.8V setting on some bulbs. After running the numbers for the chart, I have come to the conclusion that it's not a realistic expectation unless the cells are pre-heated before the discharge.

Originally Posted by Justin Case

My two workhorse bulb candidates are the MN15 and WA01274, for lower output/longer run time and higher output/moderate run time options, respectively. If I didn't have an FM MN bi-pin adapter and a bunch of 1274s already, I might go with an MN15 and MN61.

I'm taking a slight chance with my Level 3 at 8.0V for the 1274. But I can always run the bulb at Level 2 at 7.3V. At $5 per bulb, the 1274 looks like a good all-around choice to me.

I think that plan would work beautifully. My goal in setting up the recommended drive ranges was to never venture below an estimated 10 hours bulb life. The 1274 at 8V won't have a ton of bulb life, but at least at 8V, I suspect it should produce somewhat predictable behavior.

I went ahead and ran some numbers for you as I know that you like specifics (none of these numbers are truly "specific," as that would require years of testing and a lot more decimal places, but it's a ballpark to compare to the chart):

Now I see where you are getting that from. When I look at my box of the HO-M6R, it's spec is 700L @ 13V. Ain't gonna get up there with these cells.

I wish it were that simple.

At the time when bulbs designed for 3x li-ion cells started hitting the market, compared to many bulbs out there designed for 4xCR123 cell, the manufactures of these new "3xli-ion" bulbs decided to "call" them "13V" bulbs to help differentiate them from the "12V" bulbs being sold for 4xCR123 configurations. In truth, the 12V bulbs aren't 12V bulbs and the 13V bulbs aren't 13V bulbs. In the long run, I believe that all of these manufactures of tactical lamp assemblies have in a sort of way bitten themselves in the ankle by even attempting to use voltage in the nomenclature related to the bulbs themselves. Model numbers would have been better as perhaps they would not have ingrained the false sense of "understanding" that the voltage ratings did in many consumers. At the end of the day, none of those mistakes will matter because it's all going to LED, where they can make all new mistakes !!!!

The LF 3xli-ion bulbs, like the HO-M6R, D36 "13" bulbs, IMR-13, and IMR-M6, are all probably designed to hit their listed bulb lumen rating at somewhere around 11.1V at the bulb (give or take, probably give). LF lists bulb lumen and not torch lumen, so I have applied the same 0.65 conversion for them just as well.

-----------

Originally Posted by RichS

This is based upon the results of beamshot tests I did a while back with the M6. To be clear, I was referencing the throw of the HO-M6R per the prior statement. I'm not disagreeing that the MN21 puts out more overall lumens. Now, the "smokes" part came from testing the MN21 on fresh primaries (stock SureFire config) vs. the HO-M6R.

Even my lux measurements confirm that the HO-M6R can outperform the MN21 in raw throw when compared fresh off the line on good cells. However, I think if you had a chance to compare the overall performance through a discharge of a similar power bulb that runs in regulation, you would find that the constant output, color temperature, and higher CRI of the regulated bulb through the discharge winds up out-performing the HO-M6R, especially when the HO-M6R is driven by the PhD-M6 which actually hurts it's performance compared to being driven "direct drive."

Re: Feedback/impressions on the PhD-M6 custom battery pack

Yeah, I forgot about the various system resistances that suck up what little voltage leeway one might have with the 1331.

Thanks for running some estimates on the 1274. Picking 8.0V for my Level 3 is a head game battle. Should I optimize just for the 1274 and accept whatever output I get with the 1164/5607 that I also have in my inventory? If so, then I'd clearly go a little lower in voltage. Or should I also consider the 1164 and 5607 bulbs in my voltage selection, balancing 1274 performance/life with some moderate overdriving of the 1164/5607? Or optimize for the 1164/5607 (e.g., 9.0V for Level 3) and use Level 2 (7.3V) for the MN15, MN20, 1111, 64250, 1274, and 5761 (eventually, when battery technology can meet the challenge)?

I went with balancing 1274 performance/life with some moderate overdriving of the 1164/5607. The ability to fall back to Level 2 at 7.3V with the 1274 helps in that decisionmaking. I also selected a similar fall back concept for the 1111 and 5761 from Level 2 to Level 1.

Level 4 at 10.8V seems to have limited utility currently, but I'm tending toward sticking with it -- thinking to the future when there are 5V spinel Li-ions.

Re: Feedback/impressions on the PhD-M6 custom battery pack

Thanks so much for taking the time to put up the MN21 vs. MN61 beamshots Will! They were very helpful.

I have just a couple of follow-up quetions:

Since the MN61 will be the main purpose of my 9.0V level 3, based on your shots it looks like I should change this to 9.2V to get a nice white beam. Would this be your recommendation base on what you saw, or do you feel this would be pushing this bulb too close to the edge?

Also, are the above beamshots with the MN21 used at the 6.8v setting? The reason I was wondering, is my shots of the MN21 with primaries should also be running at around 6.75v, and you can see how dim it is compared to the MN21 on 2x18650s. At this voltage it even looks much dimmer than the HO-M6R. I just wanted to make sure that 6.8v is still the optimal voltage for running the MN21 based on my and your beamshots.

Eric - thanks much for your detailed explanation on the reasons this pack is less than optimal for the HO-M6R. I forgot that it was mentioned before about losing some voltage due to the additional contacts, etc. I think I'll keep the 10.8 setting for now, just to be able to run a higher voltage bulb in the future, or even the HO-M6R in a pinch. I'll still keep my DD pack for this bulb when I want to run it.

Thanks again for the lighting fast answers and all the great information you all are providing in this thread!!

Re: Feedback/impressions on the PhD-M6 custom battery pack

Originally Posted by RichS

Since the MN61 will be the main purpose of my 9.0V level 3, based on your shots it looks like I should change this to 9.2V to get a nice white beam. Would this be your recommendation base on what you saw, or do you feel this would be pushing this bulb too close to the edge?

Yes, the MN61 at 9.2 volts was awesome. I would not push it harder. In fact, back when had two of the ill-fated HDM6's, I keep one of my M6's with an MN21 and one with the MN20. Now with my own pack, and given the 3x17670 source, I am keeping one of them with the MN20 (at 7.5 volts), and for sure going to keep the other one of my M6's with the MN61 bulb at 9.2 volts.

Originally Posted by RichS

Also, are the above beamshots with the MN21 used at the 6.8v setting?

Yes, absolutely. 6.8 Vrms (regulated )

Originally Posted by RichS

The reason I was wondering, is my shots of the MN21 with primaries should also be running at around 6.75v, and you can see how dim it is compared to the MN21 on 2x18650s. At this voltage it even looks much dimmer than the HO-M6R. I just wanted to make sure that 6.8v is still the optimal voltage for running the MN21 based on my and your beamshots.

Way too many things different between your setup and mine. Even changing the manual exposure would make things brighter or dimmer - too many variables make it impossible to directly compare my beamshots to anyone else's. That being said, yes, 6.8Vrms on the PhD-M6 "is" the optimal and correct drive level for the MN21. Driving the MN21 harder will only give you even shorter cell life, more heat wasted in the cells, shorter runtimes, and a shorter life for the bulb.